Microelectronic imagers are used in digital cameras, wireless devices with picture capabilities, and many other applications. Cell phones and Personal Digital Assistants (PDAs), for example, are incorporating microelectronic imagers for capturing and sending pictures. The growth rate of microelectronic imagers has been steadily increasing as they become smaller and produce better images with higher pixel counts.
Microelectronic imagers include image sensors that use Charged Coupled Device (CCD) systems, Complementary Metal-Oxide Semiconductor (CMOS) systems, or other solid state systems. CCD image sensors have been widely used in digital cameras and other applications. CMOS image sensors are also quickly becoming very popular because they are expected to have low production costs, high yields, and small sizes. CMOS image sensors can provide these advantages because they are manufactured using technology and equipment developed for fabricating semiconductor devices. CMOS image sensors, as well as CCD image sensors, are accordingly “packaged” to protect their delicate components and to provide external electrical contacts.
FIG. 1 is a schematic side cross-sectional view of a conventional microelectronic imaging unit 1 including an imaging die 10, a chip carrier 30 carrying the die 10, and a cover 50 attached to the carrier 30 and positioned over the die 10. The imaging die 10 includes an image sensor 12 and a plurality of bond-pads 16 operably coupled to the image sensor 12. The chip carrier 30 has a base 32, sidewalls 34 projecting from the base 32, and a recess 36 defined by the base 32 and sidewalls 34. The die 10 is accordingly sized to be received within the recess 36 and attached to the base 32. The chip carrier 30 further includes an array of terminals 18 on the base 32, an array of contacts 24 on an external surface 38, and a plurality of traces 22 electrically connecting the terminals 18 to corresponding external contacts 24. The terminals 18 are positioned between the die 10 and the sidewalls 34 so that wire-bonds 20 can electrically couple the terminals 18 to corresponding bond-pads 16 on the die 10.
One problem with the microelectronic imaging unit 1 illustrated in FIG. 1 is that the die 10 must be sized and configured to fit within the recess 36 of the chip carrier 30. Dies having different shapes and/or sizes accordingly require chip carriers configured to house each type of die. As such, manufacturing imaging units with dies having different sizes requires fabricating various configurations of chip carriers and significantly retooling the manufacturing process.
Another problem with conventional microelectronic imaging units is that they have relatively large footprints. For example, the footprint of the imaging unit 1 in FIG. 1 is the surface area of the base 32 of the chip carrier 30, which is significantly larger than the surface area of the die 10. Accordingly, the footprint of conventional microelectronic imaging units can be a limiting factor in the design and marketability of picture cell phones or PDAs because these devices are continually being made smaller in order to be more portable. Therefore, there is a need to provide microelectronic imaging units with smaller footprints.